The present invention is generally related to disk drives and, more particularly, to a transformable data interface that is used in a disk drive.
Modern disk drives, particularly, hard disk drives typically utilize what is referred to as an “embedded servo” format. A disk, in accordance with this system, includes wedge-shaped regions of servo data which separate regions in which user data can be stored during write operations and retrieved during read operations. These read and write operations are coordinated and controlled, based on the servo data, in a well-known, although complex manner. One approach in attempting to improve the handling of servo data versus user data is seen in U.S. Pat. No. 6,278,568 issued to Cloke et al. (hereinafter the '568 patent), as will be discussed immediately hereinafter.
A typical hard disk drive includes a channel IC that is configured for processing information as it is received from one or more disks within the drive, as read by a transducer arrangement, and for preparing information to be stored by the drive, using the transducer arrangement. It should be appreciated that the information retrieved by the transducer arrangement is essentially analog in form. The channel IC serves to convert both analog servo information, as well as user data that is read from the disk to digital form. In this regard the '568 patent illustrates such a channel IC in FIG. 1D, indicated by the reference number 26. Such a channel IC is often interchangeably referred to in the art as a read/write channel, read/write IC or, more simply as a channel. With regard to the type of processing that is performed by the channel IC, servo data is transferred unidirectionally from the disk to the channel IC and beyond, whereas user data is bidirectional. That is, read user data travels in the same direction as servo data from the transducer arrangement to the channel. Thus, processing of the read user data and the servo data can be shared by some components in the channel. Write user data, on the other hand, passes oppositely from the channel to the transducer arrangement. User data is generally handled in the form of NRZ data in a parallel format. In the example of the '568 patent, FIG. 1D, a channel bus 38 transfers this NRZ user data, i.e., both read user data and write user data, to and from a host interface and disk controller (HIDC) 32. It is noted that this arrangement is typical of the prior art for purposes of transferring user data between a channel IC and a controller IC. It is important to understand, however, that there is other information that is needed by the controller. In particular, the controller needs the servo information. This is complicated by the fact that the servo information is not in the NRZ parallel format that is required by channel bus 38. The typical approach of the prior art, with respect to transferring servo data, is to provide dedicated physical lines between the channel and controller in order to support transfer of the servo data. The '568 patent, in contrast, takes a different approach, as will be described immediately hereinafter.
With respect to transferring servo data from channel 26 to controller 32, the '568 patent describes its approach, for example, at col. 15, lns. 17-20. The patent converts the servo data to the format of the NRZ user data and then transfers the servo data on channel bus 38 to controller 32. While this approach does limit the number of physical connections between the channel and controller, it is submitted that the conversion process and subsequent data recovery is difficult at best. For example, the channel bus operates according to its own clocking signal and protocol whereas the servo data is essentially in the form of serial data that is provided in timed relation to its own serial clock and according to a serial data protocol. Further, the '568 patent describes the transfer of servo burst data at col. 10, lns. 2-8, via a microprocessor 120 on a microprocessor bus 36 that is separate from channel data bus 38. Thus, it appears that only part of the servo data is being transferred on channel bus 38, resulting in a complex process, at best. An approach that does not require such a difficult conversion process or complexity would be desirable.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.